Conventionally, in an evaporated fuel treatment device, a dust filter is used for preventing an adsorbent in a canister from clogging by dust. The dust filter of this type is, for example, disclosed in Japanese Laid-Open Patent Publication No. 2003-252071.
The dust filter has a filtration member having a cylindrical shape. The filtration member is arranged so as to surround an inlet pipe. A dust filter in an embodiment is arranged and structured such that air flows through the filtration member in an axial direction thereof. Further, a dust filter in a modified form is arranged and structured such that air is introduced into the filtration member from an outer circumferential side in a radial direction and flows downwardly in an axial direction. Further, a dust filter in another modified form is arranged and structured such that air is introduced into a filtration member from an upper end side in an axial direction thereof and flows inwardly along a radial direction.
However, the above-mentioned dust filter may sometimes have an insufficient filtration effect. Further, the above-mentioned dust filter may generally be easily clogged.
Further, an another dust filter is disclosed in Japanese Laid-Open Patent Publication No. 02-70967. The dust filter has a plate-shaped filtration member, and the filtration member is arranged so as to close a path of a canister. In the dust filter thus constructed, air flows in a thickness direction of the plate-shaped filtration member.
However, the dust filter can be easily clogged. This may lead to increased air-flow resistance.
It is, therefore, an object of the present invention to improve a conventional dust filter.